JP3485448B2 - Prevention method of localized dew point corrosion occurring in branch pipe of exhaust gas flue - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a local dew point due to exhaust gas generated in a branch pipe connected to an exhaust gas flue for discharging exhaust gas from a refuse incinerator or the like. The present invention relates to a method for preventing corrosion. [0002] Exhaust gas generated when incinerating industrial waste and garbage discharged from companies, restaurants, general households and the like in an incinerator is discharged into the atmosphere through an exhaust gas flue and the like. Is done. Exhaust gas from such a refuse incinerator contains a large amount of water and contains a trace amount of acidic components such as hydrogen chloride. Dew point corrosion occurs. When dew-point corrosion occurs in an exhaust gas flue or the like, not only its life is shortened, but also corrosive metals and dew water are scattered into the atmosphere accompanying the exhaust gas, resulting in pollution. [0003] In order to prevent such dew point corrosion due to exhaust gas, the following method has conventionally been used.
A low-temperature portion, such as an exhaust gas flue, where dew-point corrosion is likely to occur, is heated by steam, electricity, or the like, to prevent condensation of moisture due to a temperature drop (hereinafter referred to as prior art 1). An acid-, alkali-, and heat-resistant special paint is applied to the skin of flue gas and the like, where dew-point corrosion is likely to occur, and a steel coating is used to prevent dew-point corrosion even if moisture condenses. (Hereinafter referred to as Prior Art 2). For example, as disclosed in Japanese Patent Application Laid-Open No. 9-79564, a portion where dew-point corrosion is likely to occur, such as an exhaust gas flue, is made of a high-grade corrosion-resistant steel such as stainless steel (hereinafter referred to as prior art 3). . FIG. 5 is an explanatory diagram showing an example of prior art 1. As shown in FIG. 5, a branch pipe 3 which is a branch pipe connected to an exhaust gas flue 1 in which a heat insulating layer 2 made of a heat insulating material such as glass wool is formed on the outer periphery, in the vicinity of a branch pipe connecting portion where temperature tends to be low, and A steam pipe 5 is wound around and attached to each of the inspection manholes 4 which are branch pipes connected to the exhaust gas flue 1. One end of the steam conduit 5 is connected to a steam supply pipe 6, and the other end is a steam drain pipe 7.
It is connected to the. Reference numeral 8 denotes a damper provided in the middle of the branch pipe 3, and reference numeral 9 denotes an opening / closing lid attached to the manhole 4. [0005] In the method of the prior art 1 shown in FIG. 5, a steam pipe line for winding a steam pipe 5 is installed near a connection portion of the branch pipe 3 to the exhaust gas flue 1. And a steam trap (ST) for discharging the steam drain out of the system must be installed. Therefore, a large amount of cost is required for installing and operating these facilities. Furthermore, exhaust gas flue 1
If there are low temperature branch pipes 3 and manholes 4 where dew point corrosion is likely to occur at a plurality of locations, the installation of steam conduits 5 for heating those sections becomes complicated and prevents steam leakage. Secondary maintenance such as is required. As in the prior art 2, a method of forming a coating film of a special paint on a place where dew-point corrosion is likely to occur to protect the steel is based on the periodic maintenance of the coating part, that is, from the viewpoint of the reliability of the paint. Since repainting is required and a large amount of special paint is required, there is a problem that maintenance cost is increased. Further, the method of forming a portion where dew-point corrosion is likely to occur with a high-grade corrosion-resistant steel such as stainless steel as in the prior art 3 requires a large amount of cost and a potential difference between stainless steel and ordinary steel. As a result, there is a possibility that electrolytic corrosion occurs. Accordingly, an object of the present invention is to solve the above-mentioned problems, and to provide local dew point corrosion caused by a decrease in temperature in a branch pipe connected to an exhaust gas flue for discharging exhaust gas from a refuse incinerator or the like. Is to provide a method that can be reliably and economically prevented with a simple device. According to a method of the present invention, a gas guide plate is provided in a connection between a branch pipe connected to an exhaust gas flue and the exhaust gas flue, and one end of the gas guide plate is provided at one end thereof. In the way
The other end enters the branch pipe body, and
And the one end portion is a pipe of the exhaust gas flue on the side of the branch pipe body.
Mounted close to the wall, by the gas guide plate,
After guiding a part of the high-temperature exhaust gas flowing in the exhaust gas flue into the branch pipe body, it is returned to the exhaust gas flue again, and the temperature near the connection portion of the branch pipe body is increased by the high-temperature exhaust gas. It is characterized in that local dew point corrosion is prevented. Next, the method of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view of a connecting portion between an exhaust gas flue and a branch pipe showing a first embodiment of the method of the present invention. As shown in FIG. 1, in the method of the first embodiment, an exhaust gas flue 1 in which a heat insulating layer 2 made of a heat insulating material such as glass wool is formed on the outer periphery, and a branch pipe body in which the heat insulating layer 2 is also formed. At the connection with the branch pipe 3, a part of the exhaust gas flowing through the flue gas flue 1 is guided into the branch pipe 3 near the connection section,
A gas guide plate 10 for returning the gas to the exhaust gas flue 1 and circulating it again is attached. The gas guide plate 10 has a vertical end 10a located in the exhaust gas flue 1 and a branch pipe 3 bent from the vertical end 10a.
A horizontal end 10b which is inserted horizontally into the inside, and both ends in the width direction of the vertical end 10a are fixed to the inner wall of the exhaust gas flue 1 by welding or the like, and both ends in the width direction of the horizontal end 10b. The part is fixed to the inner wall of the branch pipe 3 by welding or the like. By closing the damper 8 provided in the middle of the branch pipe 3, a part of the high-temperature exhaust gas flowing in the exhaust gas flue 1 can be partially removed as shown by an arrow in the horizontal end 10b of the gas guide plate 10. Is guided into the branch pipe 3 along the lower side of the
It reverses from the other end of 10b and is guided again into the exhaust gas flue 1 along its upper surface and circulates. In this manner, a part of the high-temperature exhaust gas flowing in the exhaust gas flue 1 is guided and circulated by the gas guide plate 10 to the vicinity of the connection portion of the branch pipe 3 where the temperature tends to be low. The temperature near the part increases. Therefore, it is possible to prevent the dew point corrosion due to the local condensation of moisture near the connecting portion of the branch pipe 3, which has conventionally occurred. FIG. 2 shows the flow of air and exhaust gas when the damper 8 of the branch pipe 3 is opened, a fluid such as air flows from the branch pipe 3 and joins the flue gas flue 1. FIG.
As shown in (1), even when the gas guide plate 10 is attached, there is no problem in the function of merging air and the like from the branch pipe 3. FIG. 3 is a vertical sectional view of a connection between a flue gas flue and a manhole, showing a second embodiment of the method of the present invention. As shown in FIG. 3, in the method of the second embodiment, an exhaust gas flue 1 having a heat insulating layer 2 formed on the outer periphery, and a heat insulating layer 2 which is a branch pipe connected to the exhaust gas flue 1 A part of the exhaust gas flowing through the exhaust gas flue 1 is guided into the manhole 4 in the connection portion with the manhole 4 in which
An inclined gas guide plate 11 for returning to the exhaust gas flue 1 and circulating again is attached. The inclined gas guide plate 11 is used for the exhaust gas flue 1
Is provided at a predetermined angle from the flue gas flue 1 toward the manhole 4 in a connection portion between the manhole 4 and
The upper end is located near the connection between the flue gas flue 1 and the manhole 4, the lower end is located inside the flue gas flue 1, and both ends in the width direction are welded to the inner wall of the flue gas flue 1. Etc. are fixed. A part of the exhaust gas flowing through the exhaust gas flue 1
As shown by the arrow, the gas guide plate 11 is guided into the manhole 4 along the lower surface side of the inclined gas guide plate 11, and is inverted by the lid 9.
It is again guided into the flue gas flue 1 and circulated. In this way, a part of the high-temperature exhaust gas flowing through the exhaust gas flue 1 is guided and circulated into the manhole 4 where the temperature tends to be low by the inclined gas guide plate 11, so that the vicinity of the connection with the manhole 4 can be obtained. Temperature rises.
Therefore, it is possible to prevent the dew-point corrosion due to the local dew condensation of water near the connection portion of the manhole 4, which has conventionally occurred. FIG. 4 is a vertical sectional view of a connection between a flue gas flue and a manhole, showing a third embodiment of the method of the present invention. As shown in FIG. 4, in the method of the third embodiment, as in the second embodiment, an exhaust gas flue 1 having a heat insulating layer 2 formed on the outer periphery and a branch pipe connected to the exhaust gas flue 1 are used. A manhole 4 with a heat insulating layer 2 formed on the same outer periphery
A gas guide plate 12 for guiding a part of the exhaust gas flowing in the exhaust gas flue 1 into the manhole 4 and returning the exhaust gas to the exhaust gas flue 1 to be circulated is installed in the connection portion with the exhaust gas flue 1. The gas guide plate 12 is vertically inserted into the manhole 4 at a predetermined interval along the lower surface of the manhole 4 by bending from the vertical end 13a located in the flue gas flue 1 and bending from the vertical end 13a. Bending plate 13 composed of horizontal end 13b
And a vertical plate 14 inserted vertically at a predetermined interval along the lid 9 and a horizontal plate 15 inserted horizontally along the manhole 4. Both ends in the width direction of the bending plate 13 are
Both ends of the horizontal plate 15 in the width direction are fixed to the inner wall of the manhole 4 by welding or the like, and both ends of the vertical plate 14 in the width direction are fixed to the inner wall of the exhaust gas flue 1 and the manhole 4 by welding or the like. 4 is detachably attached to the inner wall. A part of the exhaust gas flowing through the exhaust gas flue 1
As shown by the arrow, the gas is guided into the manhole 4 along the lower surface of the bent plate 13 of the gas guide plate 12, rises and turns between the vertical plate 14 and the lid 9, and flows along the upper surface of the horizontal plate 15. ,
It is again guided into the flue gas flue 1 and circulated. In this manner, a part of the high-temperature exhaust gas flowing through the manhole 4 is guided and circulated by the gas guide plate 12 into the manhole 4 where the temperature tends to be low. Rises. Therefore, it is possible to prevent the dew-point corrosion due to the local dew condensation of water near the connection portion of the manhole 4, which has conventionally occurred. Next, the present invention will be described with reference to examples and comparative examples. The method of the first embodiment of the present invention shown in FIG. 1, the method of the second embodiment shown in FIG. 3, the method of the third embodiment shown in FIG. 4, and FIG. By the conventional method, the combustion exhaust gas discharged from the refuse incinerator was discharged into the respective exhaust gas flue 1 under the following conditions. Exhaust gas temperature: 180 to 185 ° C. Water content: 33 to 35 vol. % Saturation temperature: 62 to 65 ° C. Average flow rate: 20 m / sec In the method (No. 1) of the first embodiment of the present invention shown in FIG. 1, point C of exhaust gas flue 1 having a diameter of 2100 to 2600 mm, diameter of 800 mm A thermometer 16 was attached to each of the points D and E of the branch pipe 3, and the steel shell temperature at each point was measured three times. For comparison, thermometers 16 were attached to the point A of the flue gas flue 1 and the point B of the branch pipe 3 in the conventional method shown in FIG. 5, respectively. Was closed, and the iron skin temperature at each point was also measured three times. Table 1 shows the measurement results. [Table 1] As apparent from Table 1, in the conventional method shown in FIG. 5, the temperature at the point A in the flue gas flue 1 is 162 to 166 ° C., whereas the temperature at the point B in the branch pipe 3 is 63. As a result, the temperature difference from the point A became 94 to 102 ° C., so that the temperature was in a temperature range where dew point corrosion due to dew condensation of water occurs. On the other hand, in the method (No. 1) of the first embodiment of the present invention shown in FIG.
While the temperature at the point is 159 to 164 ° C, the temperature at the point D of the branch pipe 3 is 145 to 149 ° C, and the temperature at the point E is 144 to 164 ° C.
146 ° C, temperature difference from point C is only 13-20 ° C
It was found that the temperature was kept in a high temperature range sufficiently distant from the temperature range in which dew point corrosion due to moisture condensation occurred. Next, in the method (No. 2) of the second embodiment of the present invention shown in FIG.
A thermometer 16 is attached to each of the F point of the exhaust gas flue 1 having a length of m, the G point and the I point of the manhole 4 having a diameter of about 600 mm, and the H point of the opening / closing lid 9, and the temperature of the steel shell at each point is measured three times. did. Table 1 also shows the measurement results. As is clear from Table 1, in the method (No. 2) of the second embodiment of the present invention shown in FIG. 3, the temperature at the point F of the exhaust gas flue 1 is 160 to 163 ° C. On the other hand, the temperatures at the points G and I of the manhole 4 and the point H of the opening / closing lid 9 are 138 to 145 ° C, and the temperature difference from the point F is only 17 to 25 ° C. The temperature was in a high temperature range sufficiently distant from the temperature range in which Next, in the method (No. 3) of the third embodiment of the present invention shown in FIG.
A thermometer 16 was attached to each of the J point of the exhaust gas flue 1 and the K point, the M point of the manhole 4 having a diameter of about 600 mm and the L point of the opening / closing lid 9, and the temperature of the steel shell at each point was measured three times. . The measurement results are also shown in Table 1. As is clear from Table 1, in the method (No. 3) of the third embodiment of the present invention shown in FIG. 4, the temperature at the point J of the exhaust gas flue 1 is 160 to 162 ° C. On the other hand, the temperatures at the K point and the M point of the manhole 4 and the L point of the opening / closing lid 9 are 110 to 118 ° C., and the temperature difference from the J point is 4
2 to 52 [deg.] C., which was lower than in the method of the first embodiment and the second embodiment. The temperatures at the K and M points of the manhole 4 and at the L point of the opening / closing lid 9 are lower than those in the methods of the first embodiment and the second embodiment.
The reason for this was that the structure of the exhaust gas flue 1 and the flow of the high-temperature exhaust gas led into the manhole 4 was not sufficient as a result of the structure becoming slightly complicated in order to secure the opening for the entrance, which is the original purpose of the present invention. Conceivable. However, the temperature drop is lower than in the case of the conventional method shown in FIG. 5, and a temperature of 100 ° C. or more is secured at any point, and it can be maintained at a temperature higher than the temperature range in which dew point corrosion due to moisture condensation occurs. found. As described above, according to the method of the present invention, a local portion caused by a decrease in temperature is formed in a branch pipe connected to an exhaust gas flue for discharging exhaust gas from a refuse incinerator or the like. Industrial demonstrable effect of reliably and economically preventing typical dew-point corrosion with a simple device is brought about.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a connection between an exhaust gas flue and a branch pipe, showing a method according to a first embodiment of the present invention. FIG. 2 is a state diagram showing a flow of exhaust gas when a fluid flows from a branch pipe and joins an exhaust gas flue in the method of the first embodiment. FIG. 3 is a vertical sectional view of a connection between an exhaust gas flue and a manhole, showing a method according to a second embodiment of the present invention. FIG. 4 is a vertical sectional view of a connection between an exhaust gas flue and a manhole, showing a method according to a third embodiment of the present invention. FIG. 5 is an explanatory view showing a connection part between an exhaust gas flue and a branch pipe, showing an example of the prior art. [Description of Signs] 1 Exhaust gas flue 2 Heat insulation layer 3 Branch pipe 4 Manhole 5 Steam conduit 6 Steam supply pipe 7 Steam drain pipe 8 Damper 9 Opening / closing lid 10 Gas guide plate 11 Gas guide plate 12 Gas guide plate 13 Bending plate 14 Vertical plate 15 Horizontal plate 16 Thermometer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-42732 (JP, A) JP-A-4-41938 (JP, U) JP-A-60-156344 (JP, U) JP-A-4-167 115230 (JP, U) Japanese Utility Model Showa 62-18319 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) F23L 17/02 F23J 15/00

Claims (1)

(57) [Claims 1] A gas guide plate is provided in a connection portion between a branch pipe connected to an exhaust gas flue and the exhaust gas flue, and one end thereof is provided.
The other end enters the exhaust pipe and the inside of the branch pipe.
And the one end is in front of the branch pipe side.
Attached so as to approach the pipe wall of the exhaust gas flue, the gas guide plate guides a part of the high-temperature exhaust gas flowing in the exhaust gas flue into the branch pipe body, and then returns to the exhaust gas flue again, A method for preventing local dew-point corrosion occurring in a branch pipe of an exhaust gas flue, wherein local dew-point corrosion is prevented by increasing the temperature near the connection part of the branch pipe by the high-temperature exhaust gas. .